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## #1 2011-03-01 02:55:32

John E. Franklin
Member
Registered: 2005-08-29
Posts: 3,588

### Let's make triangular numbers.

The first triangular number is 1.
add 2, then 3, then 4, on forever
to make triangular numbers.

So I'll go first:

1
(one)

igloo myrtilles fourmis

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## #2 2011-03-01 13:28:07

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 107,194

### Re: Let's make triangular numbers.

3 is triangular and prime.

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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## #3 2011-03-02 05:17:16

G-man
Member
Registered: 2011-02-28
Posts: 16

### Re: Let's make triangular numbers.

6  Its triangular & first composite which isn't a square.

Maths!......

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## #4 2011-03-02 09:41:30

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 107,194

### Re: Let's make triangular numbers.

10 - The number of balls in a 10 ball rack. The first 2 digit triangular number! Also it is larger than 1 - 9 and has a zero in it.

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Online

## #5 2011-03-02 12:31:13

John E. Franklin
Member
Registered: 2005-08-29
Posts: 3,588

### Re: Let's make triangular numbers.

15
5 x (6/2)

igloo myrtilles fourmis

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## #6 2011-03-02 15:17:51

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 107,194

### Re: Let's make triangular numbers.

21 everybody's favorite number

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Online

## #7 2011-03-02 15:43:46

MathsIsFun
Registered: 2005-01-21
Posts: 7,631

### Re: Let's make triangular numbers.

28: has factors 1, 2, 4, 7, 14, 28 and reminds me of February

"The physicists defer only to mathematicians, and the mathematicians defer only to God ..."  - Leon M. Lederman

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## #8 2011-03-02 15:53:48

G-man
Member
Registered: 2011-02-28
Posts: 16

### Re: Let's make triangular numbers.

36
square of product of first two consecutive primes.

Maths!......

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## #9 2011-03-02 21:13:39

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 107,194

### Re: Let's make triangular numbers.

45 - ( Colt ) the best automatic ever made.

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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## #10 2011-03-03 15:53:14

G-man
Member
Registered: 2011-02-28
Posts: 16

55..........

Maths!......

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## #11 2011-03-03 18:17:35

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 107,194

### Re: Let's make triangular numbers.

66 - the 11 the triangular number and the name of a now infamous highway here in the southwest.

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Online

## #12 2011-03-06 02:21:55

matthen
Member
Registered: 2011-03-06
Posts: 8

### Re: Let's make triangular numbers.

78

note these triangular numbers go:
...,45,55,66,78,91, quite cool that 4,5,6,7,8,9 appear in order with no interruptions!

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## #13 2011-03-06 05:49:43

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 107,194

### Re: Let's make triangular numbers.

91 The most powerful triangular number and the one that wants to be a square the most. Also it is the only one that is 7 * 13.

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Online

## #14 2011-03-22 11:31:19

John E. Franklin
Member
Registered: 2005-08-29
Posts: 3,588

### Re: Let's make triangular numbers.

105=14+91
(14/2)*15

igloo myrtilles fourmis

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## #15 2011-03-22 12:48:39

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 107,194

### Re: Let's make triangular numbers.

The 15th triangular number is 120. Which is also 5!.

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Online

## #16 2011-03-22 13:58:55

G-man
Member
Registered: 2011-02-28
Posts: 16

### Re: Let's make triangular numbers.

136.........1, 3 & 6 are first 3 triangle numbers.

Maths!......

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## #17 2011-03-22 14:28:21

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 107,194

### Re: Let's make triangular numbers.

153

Is a square away from 2 squares. 12^2 + 3^3 = 153 and 13^2 - 4^2 = 153

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Online

## #18 2011-04-05 02:21:55

John E. Franklin
Member
Registered: 2005-08-29
Posts: 3,588

### Re: Let's make triangular numbers.

171
153 + 18 = 171
(19 x 18) / 2

igloo myrtilles fourmis

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## #19 2011-04-05 02:50:56

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 107,194

### Re: Let's make triangular numbers.

190

The famous 190 Bowery St.

http://nymag.com/realestate/vu/2008/09/50481/

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Online

## #20 2011-04-16 08:29:10

John E. Franklin
Member
Registered: 2005-08-29
Posts: 3,588

### Re: Let's make triangular numbers.

210
210 = 190 + 20
210 = 14 x 15 = (21 x 20) / 2 on this post # 20.

igloo myrtilles fourmis

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## #21 2011-04-16 08:51:43

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 107,194

### Re: Let's make triangular numbers.

231

One of the permutations of 123.

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Online

## #22 2011-04-16 11:34:54

John E. Franklin
Member
Registered: 2005-08-29
Posts: 3,588

### Re: Let's make triangular numbers.

253
253 = 231 + 22 = (1 + 22)+(2 + 21)+...(9 + 14)+(10 + 13)+(11 + 12)
= 11 x 23 = (23 x 22) / 2
This triangular number can form a digital triangle with 22 rows in 3 angles differing by 120 degrees.

igloo myrtilles fourmis

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## #23 2011-04-16 14:40:42

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 107,194

### Re: Let's make triangular numbers.

276

And that is real close to 253.

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Online

## #24 2011-04-17 12:13:04

John E. Franklin
Member
Registered: 2005-08-29
Posts: 3,588

### Re: Let's make triangular numbers.

300

Yeah 300!!!!   276 + 24.    (25 x 24) / 2       A triangle with 24 rows.

igloo myrtilles fourmis

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## #25 2011-04-17 12:20:22

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 107,194

### Re: Let's make triangular numbers.

325 which is 3*5 - 2 = 13.

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Online